Spas and hot tubs have become popular home use items during the last decade. Those designed for indoor use are generally heated by auxiliary heaters powered by natural gas, propane or electricity. Outdoor spas are also commonly heated in the same manner, but could be heated using solar power such as employed for pools and shown in U.S. Pat. Nos. 3,970,069; 3,598,104; 4,312,323,; 3,411,163; 3,072,920; and 4,227,511.
Insulated covers for spas have been on the commercial market for several years and are used to reduce the energy costs associated with spa operation. Such covers have no means for heating water. Those persons who do not have elaborate solar roof top panels or space for solar racks have no current means for heating outdoor spas using energy conserving methods. Accordingly, a need exists for a solar heated spa cover which heats spa water and at the same time conserves energy.